In recent years, a walking assistance device has been developed that is fitted from an upper leg to a foot (a part beyond the ankle joint) of a user, and assists the movement of a knee joint of the user by applying torque. This type of walking assistance device comprises a foot frame, lower leg frame, upper leg frame, and actuator. The foot frame is configured such that it can be fitted onto the user's foot. The lower leg frame is connected, by a first rotary joint, such that it can rotate with respect to the foot frame. The upper leg frame is configured such that it can be fitted onto the user's upper leg. Further, the upper leg frame is connected, by a second rotary joint, such that it can rotate with respect to the lower leg frame. The actuator is capable of applying torque to the second rotary joint. In this walking assistance device, the first rotary joint rotates coaxially with the user's ankle joint, and the second rotary joint rotates coaxially with the user's knee joint. The movement of the user's knee joint is assisted by torque applied to the second rotary joint by the actuator. The operation of the actuator is controlled by a control unit.
To ensure the safety of the user in the case of the walking assistance device malfunctioning, a configuration is desired that can restrict the rotation of the second rotary joint which is driven by the actuator. E.g., a configuration is desired that, by restricting the rotation of the second rotary joint, can ensure the safety of the user in a state where the user is fitted with the walking assistance device, even if the control unit or the actuator has malfunctioned. In the present specification, “restricting the rotation” means restricting the range of rotation.
A technique of Japanese Published Utility Model Application No. H02-122792 is known as a technique for restricting the rotation of a robot joint such as the second rotary joint of the walking assistance device. A stopper mechanism is taught in Japanese Published Utility Model Application No. 1102-122792, this stopper mechanism having one rotation side fitting, one fixed stopper and two retractable stoppers. During normal operation of the robot joint, the retractable stoppers are in a retreated position and do not interfere with the rotation side fitting. Consequently, the robot joint can rotate until the rotation side fitting and the fixed stopper make contact, and the rotation range of the robot joint is regulated by the fixed stopper. In the case of wanting to restrict the rotation range of the robot joint more narrowly than the rotation range during normal operation, the retractable stoppers are made to protrude to a position where they interfere with the rotation side fitting. In this state, the robot joint can rotate until the rotation side fitting and the retractable stoppers make contact. Consequently, the rotation range of the robot joint can be restricted more narrowly than the rotation range during normal operation.